Does "ReadPublicKey("publicReceiver.k")" return the same result each time it is called? If not, then all bets are off.
Note that encrypted stuff is binary data, not text - so an operation like "new
String(encrypted stuff)" does not make sense, and will lead to unexpected results.
What do you mean by "when I execute the minutes" - are you running this code several times within a few minutes, or what?